Single-phase motors are commonly used in home appliances with small startup load, such as, clothes washing machines, dish washers, refrigerators, air conditioners or the like. In terms of the relative positions of the stator and the rotor, the single-phase motors are categorized into inner-rotor motors and outer-rotor motors. As the name suggests, in a single-phase outer-rotor motor, the stator is disposed in an interior, the rotor surrounds the stator, and a load can be directly embedded in the rotor. For the single-phase outer-rotor motor, because the stator is disposed inside the rotor, the size of the stator is limited. For facilitating the winding, teeth of the stator define therebetween slot openings with large width, such that the motor has a large cogging torque, which affects the rotor stability during rotation and produces noises.